We used to always believe that it would ruin a beer, but I think that's been shown to be a myth. I think what started it was either what happens to a keg on a hand pump if it's left out to warm up (it oxidizes from all the air that was pumped into it), or bottles left out that warmed up but skunked due to light exposure, not the warming.

Excluding extremely warm temperatures or long times at room temperature, the simple act of allowing a beer to warm to room temp and then re-cooling it shouldn't make a noticable differance.

I might be wrong, but it seems to me that besides time and UV light exposure, the quality of stored beer is probably affected by how it has been conditioned. For instance, it if has been filtered well to remove the yeast and then is force-carbonated and stored in kegs ... or is then properly transferred to bottles with a counter-pressure filler ... then I think it should last a LONG time. But if it is naturally conditioned with yeast, storage time will probably be reduced because the yeast will flocculate, eventually die, and then autolysis will set in; conventional wisdom says that cell walls begin to break down after, IIRC, a couple of months or so, and that should affect flavor. Refrigeration will probably slow the process, but it's hard to keep all that much beer cold. However, having said all of that, there are a number of commercial brews on the market which are naturally conditioned -- Chimay and Blue Moon come to mind immediately -- and I don't know how long it is between when they are bottled and eventually used. Also, higher gravity beers, like barleywines, are better with extended aging, and in that regard I've heard some brewers speak in terms of many months approaching a year or so, but I don't have that kind of patience. As a rule, I try to drink _most_ of my beers between 2 weeks and 6 weeks after bottling with natural carbonation. Special beers, like barleywines, I'll have around for from six to maybe eight months ... but I've never kept a beer even close to a year.

Well, that sounds like a good answer, but I don't think anyone really knows for sure! I've often wondered about some of the commercial bottle conditioned beers and how long have they really been setting there. Some of my beers I've had for up to 5 months and they've tasted just fine. But that's as long as I've been able to hang on to a few bottles out of each batch.

I'm relatively new to brewing and I've been trying to read up on as much as I can. And so far, my conclusion is, that there is just a few basic rules to brewing. The rest is all just speculation and opinion.

slothrob wrote:snip ... I've never had a beer go "bad" after even 2 years. ... snip

That's good to know, although I still can't envision ever being able to save beer for that long. My comment was not meant as a statement of my personal experience or any empirical evidence, but rather was a mere assumption based on the logic that when yeast cells die, they decay and empty their guts into the beer and reportedly cause off-flavors, which is apparently why many brewers recommend that beer not be kept on a yeast cake for more than a couple of months or so. Perhaps it can go for longer, but I'd be afraid to gamble a batch of beer while pressing the limit. However, there is probably proportionately a LOT more flocculated yeast in a fermenter some months after fermentation is finished, in contrast to the amount of yeast in a bottle after conditioning is finished; that, in itself, might explain why it is generally considered inadvisable to let beer set for a long time on a yeast patty. But I guess bottles are different.

I certainly didn't mean to correct you, Bill, I just thought I'd add some of my experiences for perspective.
The yeast thing is kind of confusing, because I've always heard the same things you have, but I've yet to experience the dead yeast flavor, thank goodness! You're probably right about the size of the cake playing a role. ...or maybe it's just a concern on the corporate scale.

I've also never had an oxidized beer problem with anything I've managed to hold onto for a long time (most of my beer is gone in a few months, too). I think that is one area where having yeast around can be a benefit, as they will tend to consume any oxygen that might cause damage to a filterred beer.

I've been very surprised at how well my homebrew has lasted in my "beer cellar". It does constantly change, however.